Showing papers on "Styrene-butadiene published in 1995"

Chemical Modification of Polymers: Catalytic Hydrogenation and Related Reactions

Abstract: Some of the most important commercial polymers are diene polymers, e.g., natural rubber (polyisoprene, PI) and styrene butadiene rubber SBR). Their usefulness to scientists and engineers comes not only from their desirable physical properties, but also because they may be used as a base for a variety of chemical modification reactions that are made possible because of the presence of olefinic groups within the polymers.

Short sisal fiber reinforced styrene-butadiene rubber composites

Abstract: Styrene-butadiene rubber (SBR) composites were prepared by incorporating short sisal fibers of different lengths and concentrations into the SBR matrix in a mixing mill according to a base formulation. The curing characteristics of the mixes were studied and the samples were vulcanized at 150°C. The properties of the vulcanizates such as stress-strain behavior, tensile strength, modulus, shore-A hardness, and resilience were studied. Both the cured and uncured properties showed a remarkable anisotropy. It has been found that aspect ratio in the range of 20–60 is effective for sufficient reinforcement. The mechanical properties were found to increase along and across the grain direction with the addition of fibers. The effects of fiber length, orientation, loading, type of bonding agent, and fiber-matrix interaction on the properties of the composites were evaluated. The extent of fiber orientation was estimated from green strength measurements. The adhesion between the fiber and the rubber was enhanced by the addition of a dry bonding system consisting of resorcinol and hexamethylene tetramine. The bonding agent provided shorter curing time and enhanced mechanical properties. The tensile fracture surfaces of the samples have been examined by scanning electron microscopy (SEM) to analyze the fiber surface morphology, orientation, fiber pull-out, and fiber-matrix interfacial adhesion. Finally, anisotropic swelling studies were carried out to analyze the fiber-matrix interaction and fiber orientation. © 1995 John Wiley & Sons, Inc.

Quantitative surface analysis of styrene-butadiene copolymers using time-of-flight secondary ion mass spectrometry

Abstract: The potential applicability of time-of-flight secondary ion mass spectrometry (ToF SIMS) as an independent quantitative technique has been studied using a more complicated copolymer system: styrene-butadiene copolymer, The complication of this system is that the characteristic SIMS peaks are not unique to each monomer. It has been found that quantitative information can be obtained from the relative SIMS intensities of certain characteristic peaks, i.e. m/z = 63, 89, 103 and 115 for styrene and 53, 67 and 79 for butadiene. In particular, the intensity ratios A/(A + B), where A and B represent, respectively, the above characteristic peaks of styrene and butadiene, have been found to be linearly related to the bulk styrene molar concentration, These results suggest that a sensitivity factor that is constant and independent of the copolymer composition can be defined for these peaks. However, this conclusion cannot be generalized for other SIMS peaks, such as m/z = 77, 91 and 105.

Adhesive composition for a wound dressing

Abstract: An adhesive composition suitable for wound dressing and other medical applications comprising a mixture of polyisobutylene and a rubber polymer selected from the group consisting of random styrene butadiene rubber (SBR) and halobutyl rubber so as to form a rubbery elastomer base matrix, and at least one hydrocolloid. The addition of the SBR or halobutyl rubber to the elastomer base offsets the possible degradation of the polyisobutylene upon sterilization, and therefore, helps to maintain the integrity of the composition. Water soluble hydrocolloid gums and water swellable cohesive strengthening agents are dispersed within the base matrix and may carry a pharmaceutical agent to be dispensed directly to a wound site.

Weak boundary layers in styrene-butadiene rubber

Abstract: In this paper two kinds of weak boundary layers (WBL) in synthetic vulcanized styrene-butadiene rubber are described. i) WBL produced by the presence of antiadhesion compounds of the rubber formulation (zinc stearate, microcrystalline paraffin wax). These WBL cannot be effectively removed by solvent wiping, whether followed by washing with an ethanol/water mix or not. Although this treatment allowed a significant removal of zinc stearate, the paraffin wax concentration on the surface was not greatly reduced, thus, poor adhesion of rubber was obtained. Chlorination with small amounts of ethyl acetate (EA) solutions of trichloro isocyanuric acid (0.5–5 wt% TCI/EA) and/or an extended halogenation treatment increased the adhesion strength and effectively eliminated the zinc stearate from the rubber surface. If an additional heat treatment (50°C/24h) of the chlorinated rubber was also carried out, the WBL was more effectively eliminated and the resulting adhesion was independent of the amount of chlor...

The influence of styrene–butadiene diblock copolymer on styrene–butadiene–styrene triblock copolymer viscoelastic properties and product performance

Abstract: The effects of the styrene–butadiene (SB) diblock copolymer on the viscoelastic properties of styrene–butadiene–styrene (SBS) triblock copolymers were examined in both in the the neat state and within specific product applications. The addition of the SB diblock copolymer into a pure SBS triblock copolymer resulted in a significant decrease in the plateau storage modulus and a quantitative linear rise in tan delta. In a pure triblock, in which all endblocks are anchored in polystyrene domains, all entanglements are physically trapped. The SB diblock embodies untrapped polybutadiene endblocks that are able to relax stress by chain reptation through the rubbery polybutadiene matrix. The SB diblock copolymer quantitatively lowered the microphase separation temperature (MST) of the SBS triblock copolymer. These changes in linear viscoelastic behavior manifest themselves into a reduction in the efficiency and performance of the SBS triblock copolymer in asphalt pavement binders and hot-melt adhesive blends. Specifically, the SB diblock diminished the complex shear modulus and elasticity of a polymer-modified asphalt, which translated into lower predicted rutting specification values. The increase in diblock content altered the viscoelastic response of the hot-melt adhesive blend, translating into a reduction in the shear holding power and shear adhesion failure temperature. The lack of network participation, coupled with the relaxation of the polybutadiene endblocks, accounts for the lower strength and greater temperature susceptibility of the diblock-containing systems. © 1995 John Wiley & Sons, Inc.

Tear and processing behaviour of short sisal fibre reinforced styrene butadiene rubber composites

Abstract: The tear failure and processing characteristics of short sisal fibre reinforced styrene butadiene rubber (SBR) composites were investigated. Tear strength was examined with special reference to the effects of fibre length, fibre orientation, fibre concentration and bonding agent. It was observed that the tear strength depends on all the above factors. The tear failure mechanism was analysed from fractographs taken using a scanning electron microscope (SEM). During tear testing, the composites failed by a shearing process. Microscopic examination of cracks propagating in SBR composites revealed that the amorphous SBR matrix developed cracks, leaving ligaments of rubber attached to the broken fibres. The rubber particles were stretched as the crack opened and failure occurred at large critical extensions. It was observed that an increase in the concentration of fibres increased the tear strength in both longitudinal and transverse directions. The tear strength values were almost three to four times higher than those of the unfilled vulcanizates under similar conditions. In order to analyse the processing behaviour, the green strength, mill shrinkage and Mooney viscosity of the compounds were determined. Finally, the polymer-filler interaction was studied using the Lorenz-Park and Kraus equations.

Short fibre elastomer composites: effect of fibre length, orientation, loading and bonding agent

Abstract: A series of short fibre reinforced styrene butadiene rubber (SBR) composites were prepared by incorporating sisal fibres of different lengths and different concentrations. The vulcanization behaviour and the properties of the vulcanizates were measured by the relevant ASTM procedures. The processing characteristics such as green strength and mill shrinkage were improved by the addition of fibres. The properties like tensile strength, tear strength, moduli at 10% and 20% elongations were found to be maximum for composites containing longitudinally oriented fibres of length 6 mm. Mixes containing 35 phr loading of fibres and bonding agent showed better mechanical performance than others. The failure behaviour of tensile and tear specimens have been analysed by scanning electron microscopy techniques.

Morphology and tensile properties of styrene–butadiene copolymer reinforced asphalt

Abstract: Morphology and tensile properties of several styrene-butadiene copolymer reinforced asphalts have been investigated. In all cases, the raw materials were commercial samples; for the styrene-butadiene copolymer, a branching (nonlinear) block polymeric chain of high molecular weight was used. On the other hand, the asphalt was a nonoxydized commercial sample. The raw materials were characterized prior to making the composite. The morphology and mechanical properties of composites obtained at different chemical compositions were determined, and a comparison of these experimental results to different models, according to the composite morphology, is shown. © 1995 John Wiley & Sons, Inc.

Rheological behavior of blends of natural rubber and styrene–butadiene rubber latices

Abstract: The rheological behavior of blends of natural rubber (NR) and styrene–butadiene rubber (SBR) latices has been studied with reference to the effects of blend ratio, shear rate, surface-active agents (casein and sodium carboxymethyl cellulose), and temperature. When the SBR content was less than 50%, the viscosities of the blends appeared to be a nonadditive function of the viscosities of the constituent homopolymers; i.e., a positive deviation was observed. This was due to the structural buildup of the SBR domains. The SBR domains underwent agglomeration and consequently so-called microflocculation took place. The viscosities of all the blends were found to decrease with increase of temperature and shear rate. The increase in temperature and shear rate marginally weakened the structural buildup as evidenced by the lowering of viscosity. As the SBR content in the system increased, the pseudoplasticity of the blend increased. Even in the presence of surface-active agents the blends showed composition-dependent positive deviation. However, surface-active agents marginally reduced the extent of structural buildup by reducing the microflocculation behavior of SBR domains. © 1995 John Wiley & Sons, Inc.

Use of rice-bran oil in the compounding of styrene butadiene rubber

Abstract: The compounding of rubber involves mixing of activator, co-activator, accelerator, antioxidant, filler, processing aid, vulcanizing agent, etc., to produce the rubber. The replacement of three of the above ingredients by rice-bran oil in the compounding of styrene butadiene rubber has been investigated. The higher fatty acids and phenols present in rice-bran oil act as co-activator and antioxidant, respectively, in the vulcanization process. Addition of this oil together with fillers, also meets the requirement of processing aid. The results obtained were compared with those obtained with reference mixes containing stearic acid, styrenated phenol and aromatic/napthenic oil in carbon-black and silica-filled systems. Evaluation of the cure characteristics of the mixes indicates that substitution of the above ingredients with rice-bran oil did not affect the cure properties. Vulcanizates containing the rice-bran oil also showed physical properties comparable to the reference mixes. Processability studies using a plasticorder also showed similar trends. Considering the fact that rice-bran oil is cheaper than other conventional oils used as processing aids in rubber compounding, this non-toxic natural oil can be advantageously used in rubber product manufacture.

Vegetable oils containing styrene/butadiene copolymers in combination with additional commercial polymers that have good low temperature and high temperature viscometrics

Abstract: A composition is disclosed which comprises (A) At least one oil comprising a synthetic triglyceride, a natural oil or a derivative of a natural oil; (B) a hydrogenated block copolymer comprising a normal block copolymer or a random block copolymer, said normal block copolymer made from a vinyl substituted aromatic and an aliphatic conjugated diene, said normal block copolymer having from two to about five polymer blocks with at least one polymer block of said vinyl substituted aromatic and at least one polymer block of said aliphatic conjugated diene, said random block copolymer made from vinyl substituted aromatic and aliphatic conjugated diene monomers, the total amount of said vinyl substituted aromatic blocks in said block copolymer being in the range of from about 20 percent to about 70 percent by weight and the total amount of said diene blocks in said block copolymer being in the range of from about 30 percent to about 80 percent by weight; the number average molecular weight of said normal block copolymer and said random block copolymer being in the range of about 5,000 to about 1,000,000; and (C) at least one pour point depressant. In addition to components (A), (B), and (C) the composition may also contain (D) a performance additive.

Recyclable and compostable coated paper stocks

Abstract: Recyclable and compostable coated paper stock (10) comprising a substrate (12) coated on at least one surface with a primer coat (14) and a top coat (16) both of which are water based dispersions. The primer coat (14) comprises a water based dispersion of a polymer selected from the consisting of acrylic polymers, acrylic copolymers, polyvinyl acetate, polyvinyl alcohol, poly-ethylene vinyl acetate, poly-ethylene vinyl chloride, styrene butadiene copolymers, polyvinylidiene chloride and starch. The top coat (16) comprises a water based dispersion of a polymer selected from the group consisting of acrylic polymers, acrylic copolymers, styrene butadiene copolymers and polyvinylidiene chloride. The substrate (12) is coated with a primer coat (14) prior to the application of the top coat (16) to seal the substrate (12) surface. The top coat (16) forms a film over the primer coat (14) and imparts water and grease resistant properties to the coated paper stocks (10). The invention also includes processes for making and using the invented coated paper stocks (10).

Thermal and thermoelastic properties of fast extrusion furnace (FEF) carbon black loaded SBR vulcanizates

Abstract: The effect of FEF carbon black as filler on the thermal capacity c, diffusivity a, and thermal conductivity λ, of styrene butadiene rubber (SBR) composites in the temperature range 300–420 K was studied. The filler strongly increases the thermal diffusivity, whilst strongly decreasing the thermal capacity and the thermal conductivity (except at high FEF content ≥80 phr). The influence of the filler on the thermoelastic behaviour of the same composites was also investigated. It was found that the thermoelastic temperature change (ΔT) increased with carbon black concentration as well as the entropy change per unit extension.

Poly(vinyl chloride)/styrene‐butadiene rubber blends prepared by dynamic vulcanization with nitrile rubber as the compatibilizer

Abstract: A new kind of thermoplastic elastomer is obtained by dynamic curing of PVC/SBR blends. A compatibilizer is necessary, and of three tested—NBR and two ABSs—NBR-18 is the best. Sulfur and Dicumyl peroxide were chosen as the two different curing agents for the blends. The curing agent and its concentration have a dramatic effect on the mechanical properties. Di(2-ethyl hexyl)phthalate was used as the plasticizer for PVC. Variations in the PVC and di(2-ethyl hexyl)phthalate concentrations can produce materials having a wide range of hardness and strength to meet the needs of different applications. The effects of processing parameters such as blending time and processing temperature and the effect of filler in the blend on the mechanical properties were also investigated. The material, after processing five times, showed no significant changes in physical properties. © 1995 John Wiley & Sons, Inc.

FRP composites based on different types of glass fibers and matrix resins: A comparative study

Abstract: Flexural properties, impact energy, heat deflection temperature, and resistance to thermal and hydrothermal degradation of composites based on E-glass and N-glass fibers as the reinforcing agents, and epoxy, unsaturated polyester, phenolic, and epoxy-phenolic resin systems as the matrix materials were studied and compared. As a reinforcing agent E-glass fiber is superior to N-glass fiber, particularly with respect to development of flexural strength and modulus, impact strength, and thermal resistance; N-glass fiber, however, imparts to the composites substantially higher resistance to hydrothermal degradation under boiling conditions in different chemical environments. For use of both E-glass and N-glass fibers as reinforcing agents, the general order of resistance to hydrothermal degradation for the composites based on different matrix resins is epoxy > phenolic > unsaturated polyester resin. Incorporation of a low dose of a rubbery polymer, such as styrene butadiene rubber (0.1–0.2%) and liquid polybutadiene (0.5–0.75%), in unsaturated polyester resin as the matrix resin measurably enhances impact energy of the composite. © 1995 John Wiley & Sons, Inc.

Quantitative determination of polymers in asphalt cements and hot-mix asphalt mixes

Abstract: The addition of polymers in asphalt cement has been widespread. Quantitative analysis of these polymers is essential to verify if specifications are being met. The analysis of two styrene butadiene rubber (SBR) latexes and ethylene vinyl acetate (EVA) and styrene butadiene styrene (SBS) polymers in three different asphalts was accomplished by Fourier transform infrared (FTIR) spectroscopy. Although the behavior of each SBR latex in each asphalt yielded somewhat different calibration curves, each latex-modified asphalt cement was successfully quantified. The values for latex determined by FTIR spectroscopy yielded a more linear relationship between the dynamic shear measurements and the latex concentration than the nominal values that accompanied the mixtures. Both EVA and SBS polymers were also quantified by using the analysis that was developed for the SBR latex-modified asphalt. The infrared analysis of SBR latex in asphalt was directly applied to the analysis of SBR latex in asphalt-aggregate mixes. Analysis of 3 weight percent SBR latex in asphalt concrete samples was achieved by removing the SBR latex-modified asphalt from aggregates and analyzing the latex content by FTIR spectroscopy. Three different aggregate types, gravel, granite, and limestone, were used.

Thiophosphoryl disulfides: Novel coupling agents for styrene-butadiene rubber/carboxylated nitrile rubber blends

Abstract: Thiophosphoryl disulfide was successfully used as a novel coupling agent to form a coherent blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar styrene-butadiene rubber (SBR) establishing close proximity between them through chemical bridging. The study reveals that XNBR in the presence of thiophosphoryl disulfide greatly improves the physical properties of SBR and thus acts as a reinforcing filler. It is noted that the physical properties of the vulcanizates obtained from the SBR-XNBR blend depend upon the SBR : XNBR ratio and the mode of cure. SEM studies corroborate the observed facts. © 1995 John Wiley & Sons, Inc.

Vehicle parts comprising ethylene/2-olefin/vinylnorbornene elastomeric polymers

Abstract: Motor vehicle brake parts based on an ethylene, alpha-olefin, vinyl norbornene elastomeric polymer are manufactured with more efficiency due to brake part compounds having lower viscosity, faster and fuller cures than ethylene, alpha-olefins, diene monomer compounds, where the diene monomer is other than vinyl norbornene Additionally, the brake parts based on the ethylene, alpha-olefin, vinyl norbornene elastomeric polymer have improved resistance to elevated temperature properties, and good heat aging characteristics, compared to for instance ethylene, alpha-olefin, non-conjugated diene elastomers (where the diene is other than vinyl norbornene) or styrene butadiene rubbers

Waterproof insole material

Abstract: A waterproof insole comprises a polymeric core (1) which presents a waterproof barrier and this core is laminated with a fabric layer (2,3) which contains an impregnant for enhanced bonding within any footwear manufactured with the insole material. The polymeric core is preferably in excess of 0.5mm in thickness and the impregnant comprises styrene butadiene latex, inorganic filler such as clay, water, resin and traces of ammonia, silicone and fluorocarbon.

Stabilized styrene/butadiene block copolymers

Abstract: Disclosed is a molding composition made from linear or star-shaped styrene/butadiene block copolymers produced by anionic polymerization, of general structure (A)m-X, wherein A is a block copolymer section consisting of at least one polystyrene block with a molecular mass of 3,000 to 230,000 (g/mol) and a polybutadiene block with a molecular mass of 2,000 to 30,000 (g/mol), with A having a total molecular mass of 5,000 to 300,000 (g/mol), the block transitions are sharp or blurred and, to prevent decomposition due to light, atmospheric oxygen and/or heat, the molding composition contains 0.01 to 1 wt.% α-tocopherol, 0.1 to 2 wt.% organic phosphite of the general formula RO3P, in which R is alkyl, aryl or cycloalkyl, and 0.01 to 2 wt.% sterically hindered phenol.

Investigation on the styrene-butadiene rubber cleavage with periodic acid under the influence of ultrasonic radiation

Abstract: The cleavage of styrene-butadiene rubber (SBR) with periodic acid (H5IO6) and simultaneous injection of ultrasonic radiation has been performed. Two frequencies, 25 and 40 kHz, respectively, have been used. The results demonstrate clearly that 40 kHz ultrasound radiation accelerates significantly the cleavage reaction. The “Pearl String Model” theory had been used to elucidate this process.

Effect of Hydrocarbon and Amine Diluents on the Properties of Dicumyl Peroxide Cured Styrene-Butadiene Rubber, Part I: Gum Compositions

Abstract: Gum SBR compositions containing dicumyl peroxide and either alkane (nonadecane) or amine (octadecylamine or oleylamine) diluent were prepared. Dilution caused a reduction in rheometer torque upon curing and in the resulting crosslink density based on solvent swelling. Results for each diluent were indistinguishable. However, tensile strengths and especially storage moduli were different for nonadecane- and octadecylamine-diluted vulcanizates. Added octadecylamine mildly reinforced the gum, while nonadecane lowered strength and stiffness. Furthermore, quite strikingly, octadecylamine-diluted samples had a large, low-strain storage modulus, which decreased markedly with strain amplitude (Payne effect), while vulcanizates diluted with nonadecane showed no Payne effect.

Analysis of Tire Tread Rubber Particles and Rubber Additives in Airborne Particulates at a Roadside

Abstract: Rubber particles emitted by abrasion of automobile tire tread have caused environmental pollution, and may be hazardous to our health. In this study, airborne particulate samples were collected on the glass fiber filter using high-volume air sampler at the roadside of the 2-nd Shinmei highway in Kobe. Rubber particles in the roadside atmosphere were analyzed by pyrolysis gas chromatography. The concentration of rubber particles was estimated from the total amount of styrene and isoprene, because these two compounds are pyrolysates of styrene butadiene rubber and natural rubber which are main materials for tires. These concentrations were 0.5-10.5 μg/m3, which corresponded to 0.4-6.3% of total airborne particulates. These concentrations were higher than those in other reports, because the sampling point was the roadside of the highway in this experiment. Furthermore quantitative and qualitative analyses of rubber additives (Zn-DMDTC and IPPD) in airborne particulates were carried out by HPLC, GC and MS. Zn-DMDTC, after converted into Co-DMDTC, in airborne particulates was analyzed by HPLC. The concentrations of Zn-DMDTC were 0-5.1 pg/m3. The detected amount of Zn-DMDTC did not show mutagenic activity. However, in the case of long term exposure to these tire tread particles, we must take a hazardous effect by Zn-DMDTC into consideration. On the other hand, IPPD was confirmed in none of samples by GC and MS.

119Sn‐NMR evidence for 2,1‐initiation in the anionic polymerization of butadiene with trialkyltin lithium

Abstract: Low molecular weight polybutadienes and styrene butadiene copolymers were anionically prepared with trialkyltin lithium initiator and end-capped with either hydrogen or a trialkyltin group. These polymers were prepared with a variety of microstructures. Analysis by 119Sn-NMR and comparison to model compounds showed no cis-1,4-initiation of the butadiene. The initiation sites found were trans-1,4- and both 2,1- and 1,2-additions of the tin-lithium bound to a 1,3-butadiene. At low levels of added polar modifier, the 2,1-addition predominated. The 119Sn-NMR spectra allowed the assignment of the sequence distribution associated with the nearest eight main chain carbon atoms (2-4 monomer units) adjacent to the tin end groups. No initiation could be detected involving the styrene comonomer, but incorporation of styrene was detected as the first or second unit after initiation. The reaction of the allyl-tin end groups of these polymers with 1,2-napthoquinone was followed by NMR and was used to assign the peaks associated with 1,2-addition of the trialkyltin lithium to 1,3-butadiene. © 1995 John Wiley & Sons, Inc.

Polymerization of Styrene-Butadiene Block Copolymers Using a Dicarbanion Initiator Made by the Reaction of Lithium with .alpha.-Methylstyrene

Abstract: Linear styrene-butadiene block copolymers of the polyA-block-polyB-block-polyA type (SBS) have been synthesized using a dicarbanion initiator formed by the reaction of metal lithium and α-methylstyrene. While being unable to initiate polymerization in cyclohexane and/or n-hexane, the diinitiator performed well in benzene. Various promoters such as tetrahydrofuran (THF), tetramethylethylenediamine, and hexamethylphosphoric triamide have been added during the making of diinitiators, resulting in initiators of different functionalities and activities. The presence of THF facilitated the formation of the diinitiator, and the resulting polymers made with this diinitiator have been analyzed and mechanically tested. The effect of process variables on the polymerization kinetics and molecular characteristics was also investigated.

αtocopherol-stabilized styrene/butadiene block copolymers

Abstract: A molding material comprises styrene/butadiene block copolymers obtainable by anionic polymerization and from 0.01 to 1% by weight, based on the polymer, of α-tocopherol.